Refrigerating apparatus



June 23, 1942. H. F. SMITH REFRIGERATING APPARATUS Filed Oct. 26, 1938 3 Sheets-Sheet 1 1 a INYENTOR.

ATTORNEYS Patented June 23, 1942 UNITED STAT ears OFFICE REFRIGERATING APPARATUS corporation of Delaware Application October 26, 1938; Serial-No. 237,089

2 Claims.

This invention relates to refrigeration, and more particularly to a novel refrigerant compressing mechanism.

It is an object of this invention to provide a compressor having mechanically operated valve means combined with automatic means for preventing thecompression pressure from becoming needlessly high.

In the usual form of compressor employing mechanically opierated valves, the compressor operates efliciently only at certain limited head pressures and back pressures. While it is possible to provide compressors having mechanical- 1y operated valves with means for varying the timing of the valve operation so as to increase the efliciency, such timing devices are complicated and add to the cost of construction. On the other hand, compressors employing automatic valvesrequire no special adjustment for normal changes in operating pressures. However, automatic valves are usually noisy andhave a reduced efficiency due to the fact that the operation of the automatic valve is dependent upon a change in pressure before it will operate. It is an object of this invention to provide a compressor with a simplified valve arrangement which has the advantages of a compressor employing a mechanically operated valve as well as all of the advantages of a compressor employing automatically operated valve means.

Another object of this invention is to provide a compressor having a mechanical valve arranged in parallel with an automatic valve.

Still another object of this invention is to provide a novel pressure relief means for use in combination with a compression chamber.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a. view partly diagrammatic showing the principal details of a preferred modification;

Fig 2 is a sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a fragmentary sectional view corresponding to the view shown in Fig. 2 but showing a modified piston arrangement; and

Fig. 4 is a view similar to Fig. 3 showing a still further modification.

This invention relates to a compressor suitable for use in refrigerating systems such as the one shown in Fig. 1 in which the reference character In designates the motor-compressor unit which compresses the refrigerant and discharges the same through the outlet I2 into'the condenser Hi from which the refrigerant flows into the evaporator IS in the usual manner. The flow of refrigerant from the-condenser to the evaporator is controlled by'the usual form of thermostatically controlled expansion valvel8. The motor-compressor unit comprises a. conventional motor 20 "which imparts rotation to the main drive shaft 22 in the usual manner. The motor is started and stopped by means of aswitch 24 which, for .purposes of illustration, has been shown as controlled by the evaporator temperature. The main shaft 22 is journaled in the frame member 26 and has secured thereto a disc 28 which. in turn carries a crank pin 36. The crank pin 30 imparts rotation to the piston 32 and the cylinder 34. The cylinder 34 is provided with a circular portion which encircles the stationary eccentric member 38 which is secured to the main frame member 40. This frame mem: ber 43 is in the form of a spider having upstanding projections 42 which are secured to the frame 26 by means of screws 44. As the crank pin 33 revolves about the eccentric 38 the piston 32 is caused to reciprocate relative to the cylinder 34 due to the eccentricity of member 38.

The piston 32 carries at its inner end a resiliently mounted extension 46 which is slidably mounted on the main body of the piston 32 by means of the bolt 48. A spring 5!] tends to hold the extension 46 away from the main body 32. The main body 32 is provided with air passages 52 which permit the air to freely pass into and out of the space between the piston 32 and the extension 46. The stationary eccentric is provided with an axial bore 54 through which the low pressure refrigerant enters. The bore 54 communicates with a radial passage 56 which in turn communicates with a circumferentiall disposed groove 58. The main cylinder 34 is provided with a port which communicates with the groove 58 during the intake portion of the stroke.

Referring to Fig. 2 it will be observed that as the cylinder 34 is caused to rotate in the direction of the arrow from the position shown in Fig. 2 the piston element compresses the refrigerant trapped within the compression chamber until the port 60 communicates with the groove 6% which in turn communicates with the discharge passage 68. During the normal operation of the compressor there is no relative movement between the members 32 and 46 unless and until the pressure within the compression chamber exceeds the high side pressure within the main motor-compressor housing. In the event that the pressure within the cylinder 34 exceeds the high side pressure the extension 46 will compress the spring 50, thereby increasing the effective volume of the compression chamber. At the end of the compression stroke the compressed gas is free to flow through the outlet 68 and the spring 50 will return the extension 46 to its normal position. By virtue of this novel arrangement the pressures within the compression chamber never become excessively high, even though the valve port is mechanically opened and closed. It is apparent therefore that changes in either back pressure or head pressure or both require no change in the valve timing as the compression pressure never materially exceeds the head pressure,

In Fig. 3 I have shown a somewhat similar arrangement in which all of the parts are constructed similar to the parts shown in Figs. 1 and 2 with the exception of the piston 69. In this modification, the piston 69 is a one-piece piston carried by a bell crank which is pivotally mounted on a stud 12 carried by the disc 28. A spring element 14 which has one end anchored in the stud 12 and its other end pressing against one arm of the bell crank serves to bias the piston 69- inwardly. The stroke of the piston may be varied by means of the adjusting element 16. In this modification, as the pressure within the compression chamber 34 exceeds the high side pressure within the main motor-compressor housing, the piston 69 moves radially outwardly against the tension of the spring 14 whereby the compression pressure is prevented from' becommg needlessly high.

In the modification shown in Fig. 4 all of the parts are similar to the corresponding parts in the first modification with the exception of the piston element designed by th reference character 80 which, in this modification, carries a poppet valve 82 which opens against the pressure of the spring 84 at such times when the pressure within the compression chamber exceeds the pressure within the main motor-compressor housing. The poppet valve 82 closes as soon as the pressure becomes substantially equalized and remains closed during the full suction stroke as well as the beginning of each compressor stroke. The amount of pressure difference necessary to open the poppet valve 82 is determined by the strength of the return spring 84 which needs merely be strong enough to properly seat the poppet valve. The stem of the poppet valve reciprocates within the cross member 86 secured to the'piston 80. The cross member 86 is provided with apertures 88 through which the gas may freely flow,

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A pump including a cylinder, a piston extending into the cylinder, an inlet for said cylinder, an outlet forsaid cylinder, a connection to said piston capable of yielding under abnormal compression within said pumping cylinder comprising an arm connected to said piston and yielding means for permitting movement of said arm to avert greater compression in the pump.

2. A pump including a cylinder, a piston extending into the cylinder, an inlet for said cylinder, an outlet for said cylinder, 2. connection to said piston capable of yielding under abnormal compression within said pump comprising an arm connected to said piston, pivot means for said arm, yielding means for biasing said arm in one position about said pivot and means for moving said pivot with respect to the cylinder to cause movement of the piston relative to the cylinder to accomplish pumping.

HARRY F. SMITH. 

